In various mechanical devices, and particularly within automatic vehicle transmissions, specialized overrunning or one-way clutching devices are used to produce a one-way driving connection between the respective input and output clutch races. Specifically, a one-way clutch is capable of transmitting torque when the rotation of one race with respect to the other race is in one direction, with the clutch “overrunning” or freewheeling when the rotational direction is reversed.
The relative shape and orientation of the input and output races may vary depending on the particular clutch design. Certain one-way clutches have input and output races that are oriented in a radially concentric manner with respect to each other. Alternately, the confronting or mating faces of the input and output races have a planar orientation or relationship. The mechanical means used to lock a typical one-way clutch are varied, but commonly consist of torque-transmitting elements such as rollers, sprags, rockers, or struts that are positioned between the input and output races. Depending on the particular type or style of one-way clutch and the direction of rotation, each race may contain unique surface features suitable for engaging one or more of the struts in order to selectively enable various clutch operating modes.
The operating modes of a basic one-way clutch include a “locked” mode in one rotational direction and a “freewheel” mode in the opposite rotational direction. In a basic one-way clutch, the operating mode is determined by the direction of the torque being applied to the input race. However, the increased complexity of power transmitting mechanisms has led to a class of selectable one-way clutches or SOWC. A SOWC is similar to a basic one-way clutch in operation as described above. However, as the name implies, SOWC are further capable of producing a driving connection between an input and output race in one or both rotational directions, and/or are also able to freewheel in one or both rotational directions as needed.